linux-kernel - Re: [PATCH 3/3] iommu/arm-smmu: re-enable context caching in smmu reset operation

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Date:   Sat, 4 Nov 2023 12:30:54 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bibek Kumar Patro <quic_bibekkum@...cinc.com>, will@...nel.org,
        robin.murphy@....com, joro@...tes.org, dmitry.baryshkov@...aro.org,
        a39.skl@...il.com, quic_saipraka@...cinc.com,
        quic_pkondeti@...cinc.com, quic_molvera@...cinc.com
Cc:     linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, qipl.kernel.upstream@...cinc.com
Subject: Re: [PATCH 3/3] iommu/arm-smmu: re-enable context caching in smmu
 reset operation



On 11/3/23 22:51, Bibek Kumar Patro wrote:
> Context caching is re-enabled in the prefetch buffer for Qualcomm SoCs
> through SoC specific reset ops, which is disabled in the default MMU-500
> reset ops, but is expected for context banks using ACTLR register to
> retain the prefetch value during reset and runtime suspend.
> 
> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
> ---
>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 26 ++++++++++++++++++----
>   1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 590b7c285299..f342b4778cf1 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -457,11 +457,29 @@ static int qcom_smmu_def_domain_type(struct device *dev)
>   	return match ? IOMMU_DOMAIN_IDENTITY : 0;
>   }
> 
> +#define ARM_MMU500_ACTLR_CPRE          BIT(1)
> +
> +static int qcom_smmu500_reset(struct arm_smmu_device *smmu)
> +{
> +	int i;
> +	u32 reg;
> +
> +	arm_mmu500_reset(smmu);
> +
> +		for (i = 0; i < smmu->num_context_banks; ++i) {
This loop deserves a comment above it like

/* Re-enable context caching after reset */

Konrad